Bartonella species are emerging zoonoses. This project examines the infection and coinfection prevalence of Bartonella species, Borrelia burgdorferi, and Anaplasma phagocytophilum, in field-captured rodents and ectoparasites in northern California. It further tries to develop a Peromyscus mouse infection model for Bartonella washoensis, Bartonella vinsonii subsp arupensis, Bartonella vinsonii subsp berkhoffi, and Bartonella henselae. Another step is taken to evaluate transmission cycles of Bartonella washoensis and Bartonella vinsonii subsp arupensis with laboratory transmission experiments involving hard ticks (Acari: Ixodidae) as vectors. Overall, results of these experiments will provide instrumental insight into Bartonella ransmission cycles. [unreadable] [unreadable]